Replaceable low cost flexible disks contain concentric tracks which may be spaced apart by a distance such as 20 mil (thousandths of an inch). Although higher track density would increase the total capacity of the disk, an important limitation on track density is imposed by expansion and contraction of the plastic substrate material of the disk. Two major factors in dimensional changes are hygroscopic (water absorption) and thermal expansion of the substrate, the latter being anisotropic (direction dependent). In addition, time dependent anisotropic deformations of the disk occur which further limit the maximum attainable track density. A relatively simple flexible magnetic disk memory system which compensates for dimensional changes, including anistropic changes, would facilitate the reliable utilization of higher track densities and therefore higher total data capacities of flexible disks.